Kurita Water Industries Ltd.

Taeko Nakamura

Kenji Kowata

Yoshihiko Endo

Katsumi Matsumoto

Provided is a method for operating an RO-membrane treatment system that includes an energy recovery device that recovers energy from the concentrate of an RO-membrane device and the RO-membrane treatment system that reduce the occurrence of biofouling in not only the RO-membrane device but also the energy recovery device in order to increase the energy efficiency of the entire system and operate the RO-membrane treatment system with consistency. The method includes adding at least one slime-control agent selected from a combined-chlorine slime-control agent and a stabilized-bromine slime-control agent to water that is to be treated with the reverse-osmosis-membrane device such that a residual halogen concentration in the concentrate that is to be introduced into the energy recovery device is 0.1 to 10000 mg/L as total chlorine.

Method for operating reverse-osmosis membrane treatment system

Clogging of membrane by slime adhesion is efficiently prevented and stable treatment can be carried out for a long period of time at a low cost by a small amount of chemicals without membrane deterioration and trihalomethane formation, even if applied to the water having a large number of viable cell counts and a harsh water quality by supplying water to be treated to a membrane separation apparatus, adding intermittently to the water to be treated a combined chlorine agent containing sulfamic compound, and repeating a non-addition feeding period in which water to be treated is supplied for 6-120 hours without addition of the combined chlorine agent, and an intermittent addition feeding period in which water to be treated is supplied for 0.5-40 hours under the addition of a combined chlorine agent at a biofilm exfoliating concentration in an early stage of biofilm formation during the non-addition feeding period.

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Tokyo, Japan

Taeko Nakamura